Plastic and nonmetallic article shaping or treating: processes – Direct application of fluid pressure differential to... – Corrugating
Patent
1988-08-19
1989-09-12
Thurlow, Jeffery
Plastic and nonmetallic article shaping or treating: processes
Direct application of fluid pressure differential to...
Corrugating
264515, 264167, 2642095, 4251331, 4253261, 425327, 425393, 425396, B29C 4720
Patent
active
048657972
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method for the extrusion of plastic pipes, wherein a hose formed of a plasticized plastic material is passed between a mandrel, a kernel having a substantially constant diameter and forming an extension of the mandrel, and chill moulds surrounding the mandrel and the kernel and moving in a sequence in the longitudinal direction of the apparatus; the hose is caused to be pressed against the mould surfaces of the chill moulds by press moulding; and sleeve parts are formed in the hose by pressing hose parts into recesses formed in the mould surfaces of the chill moulds and having a shape corresponding to that of the sleeve parts, said hose parts being pressed into the recesses by exposing the inner face of the hose to a higher pressure of a medium than the outer face thereof.
The ends of plastic pipes are often provided with an expanded portion, i.e. a sleeve, by means of which pipes can be joined into a pipe line. Often also extension pieces are used. Such extension pieces are short pipe pieces both ends of which are provided with a sleeve.
Today, sleeves are generally made by first heating the end of a pipe and by then pushing it on a mandrel having a diameter greater than the inner diameter of the pipe, as a result of which the end of the pipe is expanded into a sleeve. In place of a mandrel, the expansion can be made by means of a pressure medium in such a manner that the end of the pipe is pressed against an external mould by means of the medium, see e.g. German Offenlegungsschrift No. 1 801 179. The pressure medium may be a gas or a liquid.
The production methods mentioned above are slow as well as expensive. The methods are slow, because the production of pipes takes place in two steps, the step for the formation of a sleeve including heating, moulding and cooling. In addition, the pipes have to be transported to the sleeve machine and away therefrom. The methods are expensive, because the sleeves are usually formed by means of an automatic special machine. Further, the heating of the pipe end requires energy.
U.S. Pat. No. 4,003,685 discloses an apparatus for the production of corrugated plastic pipes by means of a blowing method. The apparatus comprises a nozzle, a mandrel, a projecting pipe and a plug provided at the end of the pipe for making contact with the inner face of the pipe. The pipe is provided with openings so that pressurized air can be blown into a space between the nozzle and the plug, as a result of which the plastic hose is pressed against the mould surface of the chill moulds. The mould surface of some of the chill moulds comprises a relatively large recess for the formation of sleeves in the pipe.
A drawback of this apparatus is its complicated structure and the unreliable sealing effect of the plug; further, it is not possible to provide two-layer pipes with sleeves by this method, because the inner wall would sink in even at places where this is not desirable.
The object of the present invention is to provide a method and an apparatus, by means of which sleeves can be formed in plastic pipes in a manner considerably simpler than what has been possible previously. The method according to the invention is characterized in that a space for the high-pressure medium within the hose is limited to the area of the recess of the mould by means of sealings which are formed adjacent the front and the back wall of the recess by means of plastic material positioned between the kernel and the chill moulds.
In the method according to the invention, no kind of sealing element is needed in the apparatus, because the plastic material itself acts as a sealing for the high-pressure medium space. Therefore the method can be realized at low costs. The way of sealing according to the invention is also extremely reliable since no leakages occur.
In the production of pipes having a ribbed outer face and smooth inner face, the above can be realized by creating the pressure difference when a chill mould rib positioned first after the mould recess is at the inlet point of the pla
REFERENCES:
patent: 3280430 (1966-10-01), Antrobus
patent: 3732046 (1973-05-01), Martin et al.
patent: 3743456 (1973-07-01), Cini
patent: 3751541 (1973-08-01), Hegler
patent: 3919367 (1975-11-01), Maroschak
patent: 4500284 (1985-02-01), Lupke
patent: 4509911 (1985-04-01), Rosenbaum
patent: 4534923 (1985-08-01), Lupke
patent: 4721594 (1988-01-01), Jarvenkyla 264508
Thurlow Jeffery
Uponor N.V.
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